MORPHOLOGY OF ANGIOSPERMS – Class XI Biology by TEACHING CARE online tuition and coaching classes

MORPHOLOGY OF ANGIOSPERMS – Class XI Biology by TEACHING CARE online tuition and coaching classes.

Introduction

Vegetative  parts or organs of an angiospermic plant are root, stem and leaves.

Reproductive part or organ of an angiospermic plant are flower, fruit & seed.

Types of Angiosperms on the basis of form

On the basis of form, angiosperms are of following types :

  • Herbs : These are plants which are non-woody and aerial parts are not persistent. Stem of these plants is green, delicate and short. e.g. gram, wheat.
  • Shrubs : These are woody plants and are branched near the ground, stem is not much developed into clear trunk, e.g. Rose, China-rose, Croton, Duranta, etc.
  • Trees : These are woody plants, which are branched at some height and thus have much developed trunk.
  • Culms : stem with solid nodes and hollow internodes. e.g., Bambusa (Bans).

Types of Angiosperms on the basis of life span

On the basis of life span, plants are of following types :

  • Ephemerals : Such plants complete their life cycle from seed to seed within 4 to 6 weeks. e.g., Euphorbia prostrata.
  • Annuals : Such plants which complete their life cycle within one season. e.g. mustard, rice, wheat.
  • Biennials : Such plants which complete their life cycle in two growing seasons. e.g. carrot, radish.
  • Perennials : Such plants which grow for a number of seasons or for many years, are called perennials. They may produce flowers and fruits every year (i.e. polycarpic), e.g. apple, mango, lemon some produces flowers and fruits once in life (i.e. monocarpic), e.g. Agave americana, Bambusa bamboos.

ROOT

  • It develops from radical of the embryo.
  • Its growth is positively geotropic positively hydrotropic and negatively phototrophic
  • It does not have nodes & internodes
  • Roots have root cap on its apex.
  • It grows in length by its apical meristem its growth is sub-apical.
  • Roots have unicellular root hair.

Zones or Parts of a Root

  • A root consists of four zones or regions from the lower most part to the upper most part. These are :

(i)       Root cap region

(ii)      Meristematic region or main growing region

(iii)     Zone of elongation

(iv)     Maturation zone

  • Root Cap zone : Root cap is technically called calyptra. Calyptra protects the meristematic zone of root.

(ii)      Meristematic zone : This zone is present just above the root cap. This is responsible for growth of root.

(iii)     Zone of elongation : This zone consists of elongated cells. It increases in the length of the root.

(iv)     Maturation zone : This zone is characterized by the presence of unicellular root hairs.

TYPES OF ROOTS

Roots are classified in following parts :

(i)       Tap roots

(ii)      Adventitious roots

(i)       Tap root : Tap root or primary root develops from the radicle.

Thus tap root along with its branches, i.e. secondary and tertiary roots form tap root system. It is generally found in dicotyledons.

  • Adventitious roots : These roots develop from any part of the plant instead of radicle. It is found commonly in Monocots. In adventitions root system main or primary root is not present. These roots are very thin and fibrous normally.

Modifications of roots

(i)       Conical : These roots have broad base tapering towards the apex, e.g. Daucas carota (carrot).

(ii)      Fusiform : In these roots the middle portion becomes thicker and tapers        on both the ends, e.g. Raphanus sativus (radish).

(iii)     Pneumatophores or Respiratory roots : This type of root arises from underground branches of tap root, grows in upward direction (positively geotropic) bears numerous pores (pneumathodes / lenticels). e.g., Avicennia, Sonneratia.

  • Stilt roots : In some plants roots are formed from the nodes of lowermost portion of the stem and provide mechanical support to the plant by fixing it in soil firmly, Pandanus tinctorius (screw pine), zea mays (maize), Suaccharum officinarum (sugarcane).

(v)      Epiphytic roots : Some epiphytes, e.g. orchids have aerial roots. These roots absorb moisture from atmosphere with the help of velamen tissue.

(vi)     Floating roots : These roots store air, become inflated and spongy, project above the level of water, make the plant light and helps in floating e.g., Jussiaea.

(vii)    Prop roots: Roots arise from horizontal aerial branches. Initially, they are hygroscopic. They grow vertically downwards, penetrate the soil, become thick and assume the shape of pillars. e.g., Ficus bengalensis.

(viii)   Haustorial roots : (Sucking Roots = Parasitic Roots) : These roots are produced in parasitic plants for absorption of food from the host. They act as haustoria and protruded in host tissue. e.g., Cuscuta (Amarbel)

STEM

Characteristics of Stem

This is the ascending part of the plant axis which develops from the plumule.

It is differentiated into nodes and internodes. It bears leaves and branches at the nodes.

It is positively phototrophic & negatively geotropic. Stem has multicellular stem hair.

Forms of Stem

  1. Strong Stem : This stem maintains the upright position and shows continuous and fast growth. g. Mangifera
  2. Weak Stem : This stem cannot maintain the upright position. It spreads over the surface of the ground without rooting at the nodes. It needs support to climb on the trees. e.g. Lathyrus aphaca

Modifications of Stem

In most of the plants the stem is aerial, upright and bears leaves, flowers and fruits. In some plants, however, the stem gets modified to carry out some specific functions such as perennation, vegetative propagation, and synthesis and storage of food, etc. Various modifications of stem are as follows :

(1)      Underground modifications of stem

(2)      Sub-aerial modifications of stem

(3)      Aerial modifications of stem

 

  1. Underground modifications of stem
  2. Rhizome : It is a thick, prostrate and branched stem growing horizontally beneath the soil surface. It has distinct nodes and internodes. e.g. Zingiber officinale (ginger); Curcuma domestica (turmeric) etc.
  3. Tuber : It is the swollen tip of the underground branch. The tubers are round or oval or irregular in shape. Each tuber has many ‘eyes’, which represents nodes. e.g. Solanum tuberosum (potato) and Jerusalem artichoke.
  4. Sub-aerial modifications of stem
  5. Runner : It is a slender, prostrate aerial stem creeping horizontally on the surface of the soil. At the nodes axillary buds form new aerial shoots and roots are give off on the lower surface. e.g. Cynodon (doob grass), Oxalis sp. (wood sorrel), etc.
  6. Sucker : Arising from the basal underground portion of the main stem. Initially it grows horizontally below the surface of the earth but soon grows obliquely upward forming a leafy shoot. e.g. Chrysanthemum, Mentha arvensis (mentha) etc.
  7. Stolon : Branches of some plants arise from nodes of underground portions of stem and grow in horizontal direction. It is like a runner with the difference that stolon grows horizontally below the soil surface while runner grows above the surface of soil. e.g., Colocasia.

III.      Aerial modifications of stem

  1. Stem tendril : In plants with weak aerial stem and some axillary buds, instead of developing into branches, form tendrils. e.g. Vitis (vine), Passiflora.
  2. Phylloclade : Stem or its branches become modified into flat, fleshy and green leaf-like structure with distinct nodes and internodes. Opuntia,
  3. Cladode : These are phylloclades made of only one or two internodes of a branch. In Asparagus each cladode consists of a single internode and in Ruscus it is made of two internodes. Cladodes are flat and leaf-like and perform the function of foliage leaves.

LEAF

It is the most important organ of plant, because it manufactures food. The leaf develops from the node and at least one bud is present in its axis. Usually it is green in colour. Leaves originate from shoot apical meristems and are arranged in an acropetal succession. They are the most important vegetative organs for photosynthesis.

Parts of a Typical Foliage Leaf

A typical foliage leaf has three main parts

  1. Leaf base (Hypopodium)
  2. Petiole (Mesopodium)
  3. Lamina (Epipopodium)

 

Types of Leaves

Simple and Compound Leaves

On the basis of incision of Lamina, leaves may be of two types : Simple and Compound

  1. Simple leaf : In this type, there is a single lamina which is usually entire e.g. Mango Guava, Cucurbita, Cucumber etc.
  2. Compound leaf : In this type, incision of lamina reaches up to the midrib or petiole due to which lamina is divided into several small parts known as leaflets. Compounds leaves are of two types :

(A)      Pinnately Compund leaf: In this leaf a number of leaflets are present on a common axis, the rachis, which represents the midrib of the leaf. e.g. Neem.

(B)     Palmately Compound Leaf: In this leaves, the leaflets are attached at a common point, i.e., at the tip of petiole, as in silk cotton, Bombax.

Phyllotaxy

Arrangement of leaves on main stem or branches is known as Phyllotaxy.      It is of three types: (A) Alternate, (B) Opposite and (C) Whorl

  • Spiral or Alternate : In this type, one leaf arise from each node. e.g. Mango, China-rose.
  • Opposite : In this type only two leaves are attached on each node which are opposite to each other.
  • Whorled or Verticillate : In this type more than two leaves arise from each node e.g. Three in Nerium and five or more in Alstonia.

Modifications of Leaves

Main modifications of leaf are as below:

  1. Leaf Tendrils : Leaf tendrils may be formed from the whole leaf or from a part of it e.g. Lathyrus aphaca, the whole leaf, in Pisum sativum.
  2. Leaf Spines : The whole leaf or its part may be modified into the spines. Stipules e.g. in Zizyphus and Acacia.
  3. 3. Pitcher Shaped Leaves : Leaves of some insectivorous plants are modified into pitcher to trap insects. e.g. Nepenthes and venus-fly trap.
  4. Phyllode : When, except the lamina, any other part of leaf modifies into leaf like structure, it is called as phyllode e.g. Australian acacia, (Acacia melanoxylon).

FLOWER

It is a condensed and modified shoot. Flower stalk is called pedicel. Upper part of pedicel is thalamus. Floral leaves are borne on thalamus in whorls. Calyx and corolla are accessory whorls of the flower. Androecium and gynoecium are called essential whorls of the flower.

Symmetry of the Flower

          Actinomorphic : Actinomorphic flowers can be divided (passing through center) into two equal and similar halves by any vertical plane. e.g. Mustard.

Zygomorphic : Zygomorphic flowers can be divided into two equal halves by only one vertical plane e.g., Pea,

          Asymmetrical (irregular): Asymmetrical flowers cannot be divided into two equal halves by any vertical plane e.g., Canna.

Position of floral leaves on the thalamus

Hypogyny : In a hypogynous flower the ovary occupies the highest position on the thalamus, while the stamens, petals and sepals are separately and successively inserted below the ovary. Thus the ovary is said to be superior and rest of the floral parts are inferior e.g., China rose, Mustard.

Perigyny : In this condition the margin of the thalamus grows upwards to form a cup-shaped structure called calyx tube enclosing the ovary but remaining free from it, carrying with it sepals, petals and stamens. The ovary is said to be half inferior, e.g., Rose, Prunus

Epigyny : In this type of flower all the floral parts lies below the ovary. Such ovary is called as ovary inferior. e.g., Sunflower, Cucurbits.

INFLORSCENCE

  1. Racemose (=Indefinite) = It exhibits indeterminate growth of floral axis (peduncle)
  2. Cymose (= Definite) = It exhibits determinate or limited growth of floral axis (peduncle)

The arrangement of and mode of distribution of flowers on the floral axis of plant is called as inflorescence.          Sometimes entire inflorescence is made of only one flower, then it is called as solitary.

KINDS OF INFLORESCENCE

The inflorescence has been classified into three distinct types according to the modes of branching and modification of the peduncle. These kinds are:

(I) Recemose          (II) Cymose

  • Recemose: It is characterised by indeterminate growth of peduncle and acropetal /centripetal sequence of flowers.

Main axis is elongated.

These are like; Receme, Spike, Catkin, Spadix, Spikelet etc.

Main axis is shortened

These are like: Corymb, Umbel.

(II)      Cymose: In cymose inflorescence the apical meristem of peduncle produces the first flower. Other flowers which arise later and are younger are borne on lateral branches.

  1. Uniparous-Monochasial cyme : A single lateral branch arises from the peduncle of old flower which terminates in a flower. The lateral branch also terminates in a flower. e.g., Heliotropium, Heliotropium.
  2. Biparous cyme (= Dichasial cyme) : In this case the peduncle bears a terminal flower and stops growing. This peduncle bears two bracts at a node from which arise two branches. Stellaria media, Spergula arvensis, Dianthus chinensis
  3. Multiparous cyme (= Polychasial cyme) : The peduncle bears a single terminal flower and below it more than two lateral branches arise at a node. e.g., Calotropis.
  4. Cymose Head (=capitate) : In Acacia nilotica (Keekar) and Albizzia lebbek, the peduncle is reduced or condensed to a circular disc.

Fruits

Classification of Fruits

There are three main types of fruits:

  1. Simple fruits : These fruits develop from monocarpellary ovary or multicarpellary syncarpous ovary.
  2. Aggregate fruits (Etaerio) : These fruits develop from the multicarpellary, apocarpous ovary.

III.      Composite fruits (multiple) : These fruits develop from the complete inflorescence.

Simple Fruits

These fruits can be divided into two types.

  1. Dry fruits : In these fruits pericarp is not distinguished into three layers. These are not fleshy.
  2. Succulent fruits : (Fleshy fruits): In these fruits, pericarp is distinguished into three layers: epicarp, mesocarp and endocarp. Mesocarp is fleshy or fibrous. These fruits are indehiscent, so seeds are separated after decay of the fleshy part of fruit.

Aggregate Fruits

(i)       Etaerio of follicles : Calotropis and Catharanthus, Michelia

(ii)      Etaerio of berries : Polyalthea, Annona

(iii)     Etaerio of achenes : Fragaria (strawberry)

(iv)     Etaerio of drupes : Rubus idaeus

Composite Fruits (Multiple Fruits)

These fruits develop from the complete inflorescence. These are known as infructescence.

(i)       Sorosis : These fruits develop from spike, spadix or catkin inflorescence. In jack fruit pistillate flowers are developed very close to each other around the rachis. Bracts, Perianth and seeds become simple and are used for eating. In pineapple (Ananas sativus) too, rachis, bracts and perianth are the edible parts.

(ii)      Syconus : This type of fruit develops from hypanthodium inflorescence. Receptacle becomes fleshy and many achenes develop from the pistillate flowers. e.g., Fig (Ficus carica).

Family

This is arrangement of species having similar characters.

 Monocotyledons Dicotyledonous
1See of having single cotyledons called monocotyledonous(a)Seeds having two cotyledons called dicotyledonous plants
2It includes family like :- Liliaceae, Graminae/Poacea(b)It includes family like :-

Malvaceae

Solanaceae

Caesalpinaceae

Leguminaceae

 


Solved questions

 

  1. Justify the following statements on the basis of external features :

(a)      Underground parts of a plant are not always roots.

(b)      Flower is modified shoot.

Ans.(a)Underground part of a plant are not always root. Sometimes stem or stem branches occur underground to perform some special functions e.g. Potato tuber is a underground modification of stem because it has both nodes and internodes.

(b)      Flower is modified short consisting of highly reduced stem branch to form thalamus in which the nodes are borne only towards the tip. The floral parts i.e., sepals, petals, stamens and carpels are arranged in their respective whorls and arise from nodes.

  1. Explain the following terms :

          (i)       Aleuron layer                            (ii)      Coleoptile

(iii)     Scutellum Monocot seeds

Ans.(i)         Aleuron layer : The outer covering of endosperm in separates the embryo by a protecneuron layer called aleuron layer.

(ii)      Coleoptile : In monocot seeds the plumule and radicle are enclosed in sheaths which are called coleoptile and coleorhiza respectively.

(iii)     Scutellum : are end of endosperm there is a small embryo which consist one large and shield shaped cotyledons known as scutellum.

  1. What is apocarpous and syncarpous of ovary?

Ans.   Apocarpous : When more than one carpel is present in a flower and all are free to each other called as apocarpous condition. e.g. Lotus and Rose.

          Syncarpous : When more than one carpel is present in a flower and all are united called syncarpous condition. e.g. Mustard and tomato.

  1. Differentiate fibrous rot and adventitious root.

Ans.

Fibrous RootAdventitious Root
Thread like branches of tap root, arising mainly from the various regions of the radicle, which behave in the same manner as the primary root are called fibrous rootThe roots developing from anywhere except the radicle are called adventitious root.

 

 



EXERCISE

 

VERY SHORT ANSWER QUESTIONS (1 MARK)

 

  1. What is morphology?
  2. Write two characters of root.
  3. Define the term herbs and shrubs.
  4. Give two examples of undergroup meristem.
  5. What type of venation found in banana.

 

SHORT ANSWER QUESTIONS (2 MARKS)
  1. What is phyllotaxy. How many types of phyllotaxy explain with example.
  2. Define the following terms with example :

(i)  Actinomorphic

(ii) Zygomorphic and

(iii)                        Asymmetrical flower.

  1. Give two examples of both racemose and cymose inflorescence.
  2. Classify the different types of fruits with example.
  3. Explain two modifications of adventitious roots.
LONG ANSWER QUESTIONS (5 MARKS)

 

  1. Deduce the character of stem. How many different modifications of stem?
  2. Draw a labelled diagram of flower and writes the functions of both accessary and reproductive parts.
  3. Explain with example the type of venation found in leaves of plant.
  4. Explain the following terms :

          (i)  Epigynous

(ii) Perigymous

(iii)                                                Hypogynous

  1. Draw the structure and function of fruits.

 

Pick (Ö) the correct choice :

  1. Maturation zone is characterised by the presence of

(1) Multiple root cap                  (2) Elongated cells

(3) Root pockets                        (4) Unicellular root hairs

  1. When the upper portion of root is swollen and tapers towards the lower end, the modification of root is:

(1) Nodulated                            (2) Tuberous

(3) Fusiform                              (4) Napiform

  1. Which of the following is not the function of root?

(1) Holds the soil particles together

(2) Stores food inside them

(3) Supports the plant by keeping it fixed firmly in the soil

(4) Transports absorbed water and minerals

  1. Stilt root is present in

(1) Sugarcane                           (2) Banyan

(3) Pine                                     (4) Trapa

  1. Prop roots are

(1) Tap roots                             (2) Fasciculated roots

(3) Branched roots                    (4) Adventitious root

  1. Petiole gets modified into leaf like structure and synthesizes food due to early fall of lamina in some compound leaves. This kind of petiole is called

(1) Winged petiole                      (2) Phyllode

(3) Bulbous petiole                    (4) Tendrillar petiole

  1. When lamina is rectangular i.e. long broad and with a round base it is

(1) Lanceolate type                    (2) Oblong type

(3) Cordate type                        (4) Reniform type

  1. When the apex of lamina suddenly tapers and becomes very narrow to make a tail like structure it is known as

(1) Caudate                               (2) Acute

(3) Tendrillar                            (4) Spiny

 

  1. Venation of Mangifera indica is

(1) Reticulate unicostate

(2) Reticulate multicostate convergent

(3) Reticulate multicostate divergent

(4) Parallel unicostate

  1. Zygomorphic conditions can be represented as

(1) Å                                         (2) %

(3) G                                         (4) P

 

WORKSHEET – 1

  1. What is meant by modification of root? What type of root is found in the

(i)    Banyan tree

(ii)   Turnip

(iii)  Mangrove trees

  1. Justify the following statement on the basis of features :

          (i)    Underground parts of a plant are not always roots

(ii)   Flower is a modified shoot

  1. How is pinnately compound leaf is different from palmately compound leaf?
  2. How is dry dehiscent fruit is different from fleshy fruits?
  3. Explain with examples the different types of phyllotaxy.
  4. Write the characters and floral diagram with floral formula of following family :

          (i)    Solanaceae                                  (ii)   Liliaceae

  1. Draw a well labelled diagram of monocotyledonous seed and ex plain the function of its endosperm.

WORKSHEET – 2

 

  1. Define the following terms :

(i)    Aestivation                                  (ii)   Placentation

(iii)  Actinomorphic                             (iv)   Zygomorphic

(v)    Superior ovary                             (vi)   Epipetalous stamen

  1. Differentiate between

          (i)    Recemose and cymose

(ii)   Fibrous root and adventitious Root

(iii)  Apocarpous and Syncarpous ovary

  1. Draw a labelled diagram of

          (i)    Gram seed                                  (ii)   V.S. of mainze seed

  1. Define following terms :

          (i)    Pericarp                                      (ii)   Testa and tegumen

(iii)  Micropyle                                    (iv)   Parthenocarpic fruit

(v)    Apocarpous and syncarpous

  1. State the different parts of carpel and stamen with labelled diagram.
  2. State placentation with labelled diagram.
  3. Explain the structure of ovule with the diagram showing micropyle and chalazal end.

 

WORKSHEET – 3

  1. Explain the following terms with example

(i)    Etario of berry                             (ii)   Pome

(iii)  Drupe                                         (iv)   Amphisaraca

  1. Describe modifications of stem with suitable examples.
  2. Take one flower each of the families fabaceae and solanaceae and write its semi-technical description. Also draw their flora diagram after studying them.
  3. Describe various ty pes of placentation and found in flowering plants.
  4. What is a flower? Describe the parts of a typical angiosperm flower.
  5. How does the various leaf modifications help plants?
  6. Define the term inflorescence. Explain the basis for the different types inflorescence in flowering plants.

 

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